The key underline principle of the IRS-assisted communications is to tune the radio environment (obstacles, reflectors, etc.) such that the resulting end-to-end communication channel is favorable to radio signal transmission [1]}. IRSs are artificial surfaces whose electromagnetic response can be electronically controllable. This allows IRS elements to reflect/refract signals at any desired angle. It becomes specifically beneficial in the context of upcoming 5G and 6G systems employing mmWave and Terahertz bands [2]}, [3]} where providing ubiquitous coverage is very difficult due to a high signal absorption by obstacles/wireless environment. IRSs are also important from the energy efficiency perspective as the IRSs do not involve any encoding/decoding or amplification of impinged signal while significantly improving the signal power at the intended receiver [4]}.
